In recent years, with the enhancement in the quality of the speech synthesis technology, the range of use of the speech synthesis has drastically expanded, such as in car navigation systems, in voice mail reading applications of cellular phones, and in voice assistant applications. Moreover, a service for creating a speech synthesis dictionary from the speeches of general users is also being provided. In that service, if only recorded speeches are available, a speech synthesis dictionary can be created from the speeches of whosoever.
However, if speeches are obtained in a fraudulent manner from the TV or the Internet, then it becomes possible to create a speech synthesis dictionary by impersonating someone else, and the speech synthesis dictionary is at risk of being misused.